1. Field of the Invention
The present invention relates to compositions and method for detecting latent biological markers. More specifically, this invention relates to latent fingerprint detection formulations comprising organic solvents.
2. Description of Prior Art
Fingerprints can be used to link a criminal suspect to a crime and, therefore, are one of the most valuable pieces of evidence that can be gathered at a crime scene. Fingerprints generally are classified into three categories: visible, impression and latent. While visible and impression prints can be readily seen with the unaided eye and can be documented by photography, latent fingerprints are visually undetectable without the aide of chemical, physical, or electrical processing techniques. Most latent fingerprints are invisible deposits of natural secretions of skin on the surface of an article which typically occur as impressions corresponding to the friction ridges of the skin. These secretions, which are produced by the eccrine glands, typically comprise water, soluble amino acids, peptides, salts, lipids, and the like. It is possible to transform these deposits into a visibly detectable image. When the impressions form patterns that correspond to the unique friction ridges of a person's finger, palm, etc, the latent fingerprint can be useful in dactyloscopy.
To visibly detect and analyze latent fingerprints, the residue must be processed, preferably by developing a composition comprising an imaging reagent in a carrier solvent. For example, ninhydrin, which was discovered in 1910 [Ruhemann et al., J. Chem. Soc. 1910, 97, 1438-49], has long been used to detect latent fingerprints [Oden et al., Nature, 1954, 173, 449]. More recently, other compounds, such as 1,8-diazafluoren-9-one (DFO) and 1,2-indanedione, have been used as imaging reagents for imaging latent fingerprints [see, e.g., Pounds, et al., J. For. Sci., 1990, 35(1), 169-175 and Gardener et al. J. For. Sci., 2003, 48 (6), 1-5]. Both of these imaging reagents react with the amino acids and amines derived from peptides and/or proteins (e.g., terminal amines or lysine residues) present in eccrinal secretions to produce a dye that is visually detectable. Ninhydrin, in particular, degrades amino acids into aldehydes, ammonia, and CO2 through a series of reactions. A portion of the ninhydrin is reduced into hydrindantin. A portion of the remaining ninhydrin condenses with ammonia and hydrindantin to produce an intensely blue or purple pigment, also known as Ruhemann's purple. Accordingly, when an eccrine residue exists in a pattern, such as the ridges corresponding to a fingerprint, this pigment renders the otherwise latent fingerprint into a visually detectable image. DFO also interacts with amino acids in eccrine residue to produce pale pink image. This observation image can be enhanced by using 560-620 nm light since the DFO-amino acid complex is strongly luminescent [Champod et al., “Fingerprints and Other Ridge Skin Impressions” 1st edition, CRC Press, 2004, 128-131].
In addition to an imaging reagent, such as ninhydrin or DFO, developing compositions typically include a carrier solvent. For example, certain ninhydrin formulations have used 1,1,2-trichlorotrifluoroethane (CFC-113) as a carrier solvent. [Hewlett et al., J. For. Identification, 1999, 49 (4), 338]. However, due to its negative impact on the earth's ozone layer, CFC-113 is no longer used commercially.
Hydrochlorofluorocarbons (“HCFCs”), such as 1,1-dichloro-1-fluoroethane (HCFC-141b), are also useful as carrier solvents in certain applications but have a lower ozone depletion potential (ODP) compared to CFCs. Therefore, HCFCs are used commonly as replacements for CFC carrier solvents. However, these types of compounds are also now being phased out of commercial use due to their relatively high Global Warming Potential (GWP).
While hydrofluorocarbons (HFCs) generally possess a lower GWP compared to HCFCs, identifying HFC replacement compounds that are suitable as a carrier solvent for imaging reagents is difficult. For example, HFC-4310mee has been studied as a potential replacement carrier solvent, but this compound possesses a relatively high GWP (=1500 relative to CO2) and is not effective as a carrier solvent for DFO. [Hewlett et al.]
Accordingly, there remains a need to identify carrier solvents suitable as a replacement for CFCs and HCFCs that would not have the limitations and environmental shortcomings attributed to these materials.